They wrote the CLI "GUI" in React using ink, which is all JS-only. I don't know what the Golang way of doing this would be, but maybe it's harder if you want the same result.

There are many GUI building libraries in Go. Sure, you wouldn't be writing JSX (and I agree it's an interesting idea), but it doesn't mean it's more any work to get things rendered in a terminal with other approaches, especially with these AI assistants to help you finish the boring parts.

If the UI is complicated at all, React is a well-established way to do that easily. The one-off tools will be harder, and even the AI won't know them as well as it knows React.